How To Build A Flutter App Using MVC Architecture

Introduction

This tutorial shows how to build a Flutter app using the Model-View-Controller (MVC) architecture. MVC is a proven pattern for organizing code in mobile development: models hold data, controllers handle business logic, and views render UI. Applying MVC in Flutter keeps widgets thin, isolates state changes, and simplifies testing. We'll implement a small counter app that demonstrates folder layout, model design, controller responsibilities, and view composition.

Project Structure

A clear folder layout improves maintainability. For MVC in Flutter, use a structure like:

• lib/models/

• lib/controllers/

• lib/views/

• lib/main.dart

Models are pure Dart classes representing data. Controllers encapsulate logic and expose methods the view calls. Views are Flutter widgets that subscribe to controller outputs. Avoid stuffing network or database code into widgets — place it in controllers or separate services used by controllers.

Model Implementation

Models should be immutable or have controlled mutation. Keep them simple and focused on data. For example, a counter model might only hold an integer value and convenience methods for serialization if needed.

class CounterModel {
  final int value;
  const CounterModel(this.value);

  CounterModel incremented() => CounterModel(value + 1);
}

This model is small, testable, and has no UI code. In larger apps, models represent entities from APIs or local storage and include parsing logic.

Controller And Business Logic

Controllers mediate between models and views. They handle events, update models, and notify views. In Flutter, controllers often extend ChangeNotifier or use Streams for updates. Keep controllers free of BuildContext to reduce coupling.

Example controller using ChangeNotifier:

import 'package:flutter/foundation.dart';

class CounterController extends ChangeNotifier {
  CounterModel _model = const CounterModel(0);
  CounterModel get model => _model;

  void increment() {
    _model = _model.incremented();
    notifyListeners();
  }
}

This controller owns state and exposes methods for views to call. It can wrap repository calls and map network responses to models. For asynchronous work, use async/await and notify listeners after state transitions (loading, success, error).

View And Widget Composition

Views are widgets that render model data and call controller methods in response to user interaction. Prefer stateless widgets when possible: let controllers manage state. Use Provider, Riverpod, or simple InheritedWidget to inject controllers into the widget tree. The view subscribes to controller changes and rebuilds accordingly.

Minimal view wiring with Provider (conceptual):

• Provide the controller at app root.

• Build widgets that read controller.model and call controller.increment().

Example widget usage (conceptual code):

• Scaffold with a Text showing controller.model.value.

• FloatingActionButton that calls controller.increment().

Keep widgets focused: layout and rendering only. Move formatting, validation, and transformation logic to controllers or helpers.

Error Handling And Asynchronous Operations

Controllers should encapsulate error handling for network or storage operations. Represent UI state with a simple enum or sealed classes (loading, data, error). The view reacts to state changes and shows loading indicators or error messages.

Example approach:

• Controller exposes status and optional error message.

• View shows CircularProgressIndicator when status == loading.

• On error, display a SnackBar or inline message and allow retry via controller method.

This approach keeps mobile development flows consistent and testable: unit tests can drive controllers through success and failure scenarios without involving widgets.

Testing And Maintenance

Test controllers and models in isolation. Write unit tests that exercise controller methods, simulate repository responses, and verify notifyListeners is called or model changes as expected. Use widget tests for views that depend on controllers to verify UI reacts correctly to states.

Maintenance tips:

• Keep controllers small and focused. Split responsibilities by feature rather than by layer when features grow.

• Avoid putting navigation logic inside controllers that depend on BuildContext; instead, expose navigation intents the view interprets.

• Use dependency injection for repositories to make controllers testable.

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Conclusion

Applying MVC in Flutter helps separate concerns: models hold data, controllers implement business logic and state transitions, and views render UI. For effective mobile development, keep controllers free of UI code, prefer immutable or controlled models, and compose small, focused widgets. Use Provider or another DI mechanism to inject controllers, unit test controllers, and keep the UI responsive to controller state. With these patterns, your Flutter app will be easier to maintain, test, and scale.